Repairing material of a brick

ABSTRACT

Disclosed herein are a refractory repairing material for repairing a brick comprising a mixture of 70 to 80 wt % of alumina having not more than 1 mm of grain size, which comprises 25 to 30 wt % of the above amount with a grain size not passing through a 325 mesh and 45 to 50 wt % of the above amount with a grain size passing through a 325 mesh; 1 to 7 wt % of carbonaceous material having a grain size passing through a 60 mesh; 1 to 5 wt % of magnesia having a grain size passing through a 325 mesh; and 10 to 25 wt % of aluminum phosphate, and a method of repairing a plate-like brick.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation-in-part of application Ser.No. 07/211,837 filed on June 27, 1988, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to a repairing material of a brick and amethod of repairing a brick, and more particularly a brick used in adevice for controlling a flow rate of high temperature liquid materialssuch as molten steels.

A method of repairing a brick of this type has been known, for example,in Japanese Patent Publication No. (KOKOKU) 60-47230. In this method,the brick is detached and, after cooling the brick, repairing materialis coated to a damaged portion and then dried, in which the repairingmaterial comprises a mixture of 50 to 60 wt % of alumina, 20 to 30 wt %of sodium silicate and 20 to 30 wt % of graphite lubricant.

In this method, since the repairing material is merely coated to thedamaged portion and dried, the bondability is poor and the repairingmaterial is easily peeled off upon re-use under severe workingconditions such as the sliding force of the brick, thus this method canprovide no sufficient effect. In addition, this method can be appliedonly to those cases where the damage is slight. The repair is difficultor almost impossible for those bricks having severe, damage, forexample, damage formed to the sliding surface portion in the form of arecess of about 4 to 5 mm. Accordingly, the regenerating ratio is 20 to30% at the most.

Use of sodium silicate or graphite as the repairing material ispreferred, but, since the addition amount of the repairing material isas much as 20-30 wt %, the corrosion resistance at the repaired portionis poor and the mechanical strength is also low. Accordingly, althoughthe brick can be regenerated, the result of use is not satisfactory.

As a result of the present inventors' studies in order to solve theabove-mentioned problems, it has been found that by filling a mixture of(1) 70 to 80 wt % of alumina having a grain size of not more than 1 mm,wherein the alumina is composed of 25 to 30 wt % of the above amountwith a grain size not passing through a 325 mesh and 45 to 50 wt % ofthe above amount with a grain size passing through a 325 mesh, (2) 1 to7 wt % of carbonaceous material having a grain size passing through a 60mesh, (3) 1 to 5 wt % of magnesia having a grain size passing through a325 mesh and (4) 10 to 25 wt % of aluminum phosphate, into a damagedpart of the brick while maintaining a temperature of the brick of lessthan about 100° C., and hardening the filled mixture, the repair can bemade easily, the damage to considerable extent can be repaired with theregenerating ratio of about 100%, the repairing material can providesufficient corrosion resistance and high strength, and a working life ofthe brick can be extended. The present invention has been attained basedon the findings.

SUMMARY OF THE INVENTION

In a first aspect of the present invention, there is provided arefractory repairing material for repairing a plate-like brick used in asliding gate for controlling a flow rate of high temperature liquidmaterial, comprising a mixture of:

70 to 80 wt % of alumina having not more than 1 mm of grain size, whichcomprises 25 to 30 wt % of the above amount with a grain size notpassing through a 325 mesh and 45 to 50 wt % of the above amount with agrain size passing through a 325 mesh;

1 to 7 wt % of carbonaceous material having a grain size passing througha 60 mesh;

1 to 5 wt % of magnesia having a grain size passing through a 325 mesh;and

10 to 25 wt % of aluminum phosphate.

In a second aspect of the present invention, there is provided a methodof repairing a plate-like brick used in a sliding gate for controlling aflow rate of high temperature liquid material, comprising the steps of:

mixing 70 to 80 wt % of alumina having not more than 1 mm of a grainsize, which comprises 25 to 30 wt % of the above amount with a grainsize not passing through a 325 mesh and 45 to 50 wt % of the aboveamount with a grain size passing through a 325 mesh, 1 to 7 wt % ofcarbonaceous material having a grain size passing through a 60 mesh, 1to 5 wt % of magnesia having a grain size passing through a 325 mesh and10 to 25 wt % aluminum phosphate, thereby producing a refractoryrepairing material,

filling said produced repairing material into a damaged part of saidbrick while maintaining a temperature of said brick of less than about100° C., and

hardening said filled repairing material which is spontaneous.

The object of the present invention is to provide a repairing materialwith less carbonaceous material and without sodium silicate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a damaged plate brick;

FIG. 2 is a longitudinal cross sectional view of the damaged platebrick;

FIG. 3 is a longitudinal cross sectional view of the plate brick throughwhich a ring is inserted and;

FIG. 4 is a longitudinal cross sectional view illustrating the repairedplate brick after withdrawing the ring.

DETAILED DESCRIPTION OF THE INVENTION

A refractory repairing material for repairing a plate-like brick used ina sliding gate for controlling a flow rate of high temperature liquidmaterial according to the present invention, comprising a mixture of;

70 to 80 wt %, preferably 70 to 75 wt % of alumina having not more than1 mm of grain size, which comprises 25 to 30 wt % of the above amountwith a grain size not passing through a 325 mesh and 45 to 50 wt % ofthe above amount with a grain size passing through a 325 mesh;

1 to 7 wt %, preferably 1 to 3.5 wt % of carbonaceous material having agrain size passing through a 60 mesh;

1 to 5 wt %, preferably 1.5 to 3.5 wt % of magnesia having a grain sizepassing through a 325 mesh; and

10 to 25 wt %, preferably 20 to 25 wt % of aluminum phosphate.

As the alumina (Al₂ O₃), used in the present invention, alumina havingthe grain size of not more than 1 mm which comprises 45 to 50 wt %,preferably 45 to 48 wt % of the above amount with a grain size passingthrough a 325 mesh and 25 to 30 wt %, preferably 25 to 28 wt % of theamount with a grain size not passing through a 325 mesh is used.Although the strength is poor when only alumina having a grain sizepassing through a 325 mesh is used, the strength can be increased bymixing alumina having the grain size not passing through 325 mesh andnot more than 1 mm.

As the carbonaceous material used in the present invention, naturalgraphite, carbon black, pitch powder may be exemplified. If thecarbonaceous material is contained by more than 7 wt %, the repairingmaterial is liable to be abrased and reduce the strength.

If the content of magnesia (MgO) is less than 1 wt %, the material isless hardenable and as a result the strength thereof is insufficient.Further the adhesion of the material to the brick worsens and theseparation of the material occurs during the using. If it exceeds 5 wt%, the hardening speed increases to worsen the workability.

The aluminum phosphate is used as the binder and, if the content is lessthan 10 wt %, the fluidity is worsened and, if it is more than 25 wt %,the material becomes porous to worsen the corrosion resistance andreduce the workability.

According to the present invention, in the case of a cradle, a workinglife which has been about 3 to 5 times by using the conventionalrepairing material can be extended to 6 to 10 times by using therepairing material according to the present invention.

In the case of a tundish, a working life which has been 1 to 2 tries byusing the conventional repairing material can be extended remarkably to2 to 4 tries by using the repairing material according to the presentinvention.

According to the present invention, the repair can be made easily andeven the damage to considerable extent can be repaired with theregenerating ratio of about 100%. The repairing material is mainlycomposed of the alumina and contains no such ingredients as degradingthe properties of the repairing material and can provide sufficientcorrosion resistance. Further, since high strength can be obtainedaccording to the present invention by the reaction between the magnesiaand the aluminum phosphate, sufficient function as the plate bricks canbe obtained.

The present invention will be more precisely explained while referringto Examples as follows.

However, the present invention is not restricted to Examples undermentioned. From the foregoing description, one skilled in the art caneasily ascertain the essential characteristics of this invention, andwithout departing from the spirit and scope thereof, can make variouschanges and modifications of the invention to adapt it ot various usagesand conditions.

EXAMPLE

A plate-like brick 1 is placed on a substrate block 6. There is adamaged portion 2 on the upper surface and the bored portion 3 of thebrick 1. A ring 5 with a diameter slightly smaller than that of thebored portion 3 is inserted through the bored portion 3 and repairingmaterial 4 is filled and hardened.

Since the ring 5 with the diameter slightly smaller than that of thebored portion 3 is used and the repairing material 4 is filled from theperiphery of the ring 5 to the damage portion 2 at the upper surfacewhile the brick 1 is in a hot state at a high temperature lower thanabout 100° C. or a cold state at a low temperature like a roomtemperature, and then hardened there, the bondability with the brick 1is satisfactory. The bored portion 3 and the upper surface of the brick1 are generally damaged remarkably because of the discharge of themolten steels and sliding contact between each other.

After taking out the brick 1 from the device for controlling the flowrate of molten steels and removing obstacles such as deposited basemetals and slugs, the ring 5 with the diameter slightly smaller thanthat of the pore of the bored portion 3 is inserted, in which therepairing material 4 at the blending ratio as shown in Table 1 is filledand hardened. The examples 5 and 6 are performed for a comparison withthe examples 1 to 4 of the preferred embodiments. Then the brick 1 isused again. Although natural graphite, carbon black or pitch powder isused as the carbonaceous material, similar result can also be obtainedby any of those materials.

                                      TABLE                                       __________________________________________________________________________    Blending ratio for Repairing material (wt %)                                  Alumina (wt %)        Carbona-                                                Not passing passing   ceous     Aluminum                                      through     through                                                                             Total                                                                             material                                                                           Magnesia                                                                           phosphate                                                                           Result of use                           a 325 mesh  a 325 mesh                                                                          amount                                                                            (wt %)                                                                             (wt %)                                                                             (wt %)                                                                              after repair                            __________________________________________________________________________    Example 1                                                                           25    48    73  1.5  3.5  22    3 to 5 times for cradle,                                                      2 to 4 times for tun-                                                         dish: slight damage                     Example 2                                                                           28    45    73  3.5  1.5  22    3 to 5 times for cradle                                                       2 to 4 times for tun-                                                         dish: slight damage                     Example 3                                                                           30    45    75  6    4    15    same extent of life as                                                        Examples 1 and 2:                                                             somewhat damage                         Example 4                                                                           30    50    80  3.5  1.5  15    same extent of life as                                                        Examples 1 and 2:                                                             somewhat damage                         Reference                                                                           30    45    75  3    --   22    only 1 to 2 times of                    Example 1                             life for cradle, not                                                          usable; not practiced                                                         for tundish: remarkable                                                       damage                                  Reference                                                                           30    50    80  5    --   15    only 1 to 2 times of                    Example 2                             life for cradle, not                                                          usable; not practiced                                                         for tundish: remarkable                                                       damage                                  __________________________________________________________________________

What is claimed is:
 1. A refractory repairing material for repairing aplate-like brick used in a sliding gate for controlling a flow rate ofhigh temperature liquid material, consisting essentially of a mixtureof:70 to 80 wt % of alumina having a grain size of 1 mm or less, whichcomprises 25 to 30 wt % of the above amount having a grain size ofgreater than 325 mesh and 45 to 50 wt % of the above amount having agrain size passing through a 325 mesh; 1 to 7 wt % of carbonaceousmaterial having a grain size passing through a 60 mesh; 1 to 5 wt % ofmagnesia having a grain size passing through a 325 mesh; and 10 to 25 wt% of aluminum phosphate.
 2. A refractory repairing material according toclaim 1, wherein said mixture comprises 70 to 75 wt % of alumina havinga grain size of 1 mm or less, which comprises 25 to 28 wt % of the aboveamount having a grain size of greater than 325 mesh and 45 to 48 wt % ofthe above amount having a grain size passing through a 325 mesh; 1 to3.5 wt % of said carbonaceous material; 1.5 to 3.5 wt % of saidmagnesia; and 20 to 25 wt % of said aluminum phosphate.